Silicon‐Bridged Bi‐ and Tridentate Lewis Acidic Host Systems

Connecting multiple organic spacer functions via silicon core units leads to various organosilanes that are excellently suited as backbones for poly‐Lewis acids (PLAs). Using ethynyl spacer groups, rigid bis‐ and tris‐dioxabenzoborole (BCat)‐substituted PLAs were prepared. The fixed orientation of the Lewis acidic functions of the PLAs is reflected in their solid‐state structures. Further flexible PLAs were obtained by hydroboration of vinylsilanes using 9‐borabicyclo[3.3.1]nonane (9‐BBN), which shows the flexibility of the backbone motif. Host‐guest experiments of the bidentate representatives with pyridine demonstrate the ability of both PLA‐types (BCat or 9‐BBN) for complexing neutral guest molecules. The rigid host system shows additionally a 1 : 1 adduct formation using a bridged diamine as guest compound.